Philippe is becoming Belgium's seventh king since independence. Herewith a list of the monarchs who have headed The House of Belgium:
Leopold I (1831 to 1865) - A German prince who fought in the Russian tsar's battles against Napoleon, Leopold, the founder of the Belgian line of the House of Saxe-Coburg-Gotha, was the uncle of Britain's Queen Victoria and was elected king of the Belgians by the National Congress that declared independence from The Netherlands in October 1830.
After refusing the throne in Greece, Leopold took the oath of office on July 21, 1831. He married Louise-Marie d'Orleans, daughter of French king Louis-Philippe.
Leopold defended the young nation, repelling a Dutch invasion in August 1831 and using his relations to thwart efforts by French emperor Napoleon III to annex Belgium.
Leopold II (1865-1909) - Controversial coloniser of what is now the Democratic Republic of Congo.
Son of Leopold I, he became Belgium's second king at the age of 30.
From 1876, Leopold II pushed for exploration of central Africa, calling notably on British explorer Henry Morton Stanley.
In 1885, the Berlin Conference recognised the Congo Free State, with Leopold II as its king.
Deplorable conditions there subsequently led to an international outcry, and Leopold II ceded his personal colony to Belgium a year before his death.
He was also called the construction king because he helped transform the cities of Brussels and Ostend with major architectural projects.
Albert I (1909-1934) - The knight king. He took the throne when his uncle, Leopold II, died without leaving an heir, and faced the task of defending Belgium in World War I.
After a German invasion in August 1914, Albert I took personal command of the Belgian army, and was forced to withdraw to a small strip of land behind the Yser river in northwestern Belgium.
His action in holding that ground was widely used in official propaganda campaigns and led to Albert's quasi-legendary status of "knight king".
He also supported the right to vote for all Belgian males, which took effect in 1919, and equal status for the French and Dutch languages in Belgium.
A keen climber, Albert I died following a fall in southern Belgium in 1934.
Leopold III (1934-1951) - Controversial king of World War II.
Son of Albert I, the first years of his reign were marked by the death of his popular wife, Astrid, born princess of Sweden, after a car driven by the king crashed in Switzerland in 1935.
Eighteen days after Germany invaded Belgium in May 1940, the king capitulated unconditionally and refused to follow the Belgian government into exile.
A year later he married Lilian Baels.
When allied forces landed in France in June 1944, the king and his family were taken to Germany and then to Austria were they were freed in 1945 by US forces.
Some Belgians refused to welcome him back to the country however, and his brother, prince Charles became regent, while the royal family settled in Switzerland.
Leopold's return to Belgium in 1950 sparked violent strikes and he was forced to abdicate in favour of his eldest son, Baudouin.
Baudouin I (1951-1993) - The longest reign.
Baudouin was only 21 with he succeeded his father on the throne, and remained under his father's influence until after he married Spanish-born Fabiola de Mora y Aragon in 1960.
Brussels accorded Congo its independence that year as well, amid general strikes in Belgium.
A devout and austere Catholic, Baudouin was concerned with rising tensions between Flemish- and French-speaking Belgians.
In 1990, citing personal convictions, the king refused to sign a law that would lift penalties against abortion.
The government dug up a constitutional loophole to declare his "impossibility to reign" for two days, during which the law was passed.
Baudouin I died of a heart attack on July 31, 1993 during a holiday in Spain at the end of 42 years on the throne.
Albert II (1993-2013) -- was never supposed to be king but grew into the role.
Although Albert II did not appear to be very interested in politics, he played a pivotal role as mediator during crises between Flemish- and French-speaking Belgians, in particular in 2011, helping end the country's longest crisis when it remained 541 days without a government.
Though a committed Roman Catholic, he did not oppose laws that authorised euthanasia and same-sex marriage.
He and his Italian-born wife Paola have three children, Crown Prince Philippe, Princess Astrid and Prince Laurent.